1. Technical Field
The present invention relates to a printer that can move a platen that defines the printing position where a print head prints on a recording medium to a position removed from the printing position so that the recording medium transportation path is open at the printing position. More particularly, the invention relates to a printer that can position a platen movably supported by a platen support mechanism to the printing position in a specific posture.
2. Related Art
When loading roll paper in a roll paper printer, the cover of the roll paper compartment must be opened, the roll paper loaded, and the recording paper must be pulled from the roll and threaded through the recording paper transportation path passed the printing position of the print head. To simplify loading the recording paper, the platen, which determines the printing position, may be configured to move with the cover so that when the cover opens the platen separates from the printing position (from the print head disposed on the printer housing side) and the recording paper transportation path is open.
Japanese Unexamined Patent Appl. Pub. JP-A-2009-95993 and Japanese Unexamined Patent Appl. Pub. JP-A-2007-175911 teach platen support mechanisms that support a platen frame on which the platen is carried by means of a four joint parallel linkage mechanism disposed on each side of the platen frame. This platen support mechanism causes the platen frame to move in the front-back direction of the printer between a closed position where the platen is positioned to the printing position and an open position separated from the closed position while the platen frame, and more specifically the platen, is held in a constantly horizontal posture.
A problem with these platen support mechanisms that use a linkage mechanism is that play develops in the joints between the links over time. As a result, when the cover is closed and the platen is positioned to the printing position, play in the platen support mechanism may result in the platen or platen frame not being set to the desired specific posture. If the platen is positioned at an angle to the print head instead of in the desired horizontal posture, and the print head is an inkjet head, print quality will drop because the gap between the recording paper conveyed over the platen surface and the ink nozzle surface of the print head is not constant. In addition, if the platen frame is not supported in the specified position when the platen is positioned to the printing position, parts on the platen frame may interfere with the print head, for example, and cause other problems.
With the platen support mechanism taught in JP-A-2009-95993, a pair of protrusions are formed at the front part of the platen frame on opposite sides widthwise to the printer, and the platen is positioned to the printing position by engaging the pair of protrusions in matching channels disposed to the printer frame when the cover closes. However, because this positioning method cannot control the inclination of the platen frame in the front-back direction of the printer when positioning the platen, the platen frame is not supported in the specified posture and the platen becomes tilted in the front-back direction of the printer when play develops in the platen support mechanism.
With the platen support mechanism taught in JP-A-2007-175911, a guide roller is disposed at the back end part of the platen frame on one side widthwise to the printer, and the platen is positioned to the printing position when the cover is closed by causing the guide roller to ride onto a positioning member formed on the printer frame. However, because this positioning method cannot control the inclination of the platen frame in the front-back direction of the printer when positioning the platen, the platen frame is not supported in the specified posture and the platen becomes tilted in the front-back direction of the printer when play develops in the platen support mechanism.